Cesium potassium fluoroaluminate

Endpoint summary

Description of key information

Based on its water-solubility and the effects observed in rats upon subacute oral exposure and acute inhalation exposure, the substance is expected to be absorbed by the gastrointestinal and respiratory tract. In the absence of substance-specific data, a default absorption value of 100% is assumed for the inhalation and oral route. Skin penetration of cesium potassium fluoroaluminate of 0.72% is considered as worst-case situation for workers.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

0.72

Absorption rate - inhalation (%):

100

Additional information

No data are available that describe the toxicokinetics of cesium potassium fluoroaluminate, therefore relevant substance properties and data from toxicity studies indicating systemic bioavailability were taken together to assess the general toxicokinetics of the substance. Cesium potassium fluoroaluminate is a salt with a water solubility of 6.0 g/L at neutral pH. Once dissolved, the substance dissociates into cesium, potassium and fluoroaluminates.

Oral and respiratory absorption

The available acute oral toxicity studies (dose levels: 2000 mg/kg bw) did not reveal any effects which indicate systemic availability of the substance. However systemic effects were observed in a combined 28 -day repeated dose toxicity study with the reproduction/developmental toxicity screening test that was conducted with cesium potassium fluoroaluminate by oral gavage.

In the acute inhalation studies with the structural analogues multi constituent aluminium potassium fluoride (single exposure of 1 hour to 4.92 mg/L) and cesium tetrafluoroaluminate (single exposure of 4 hours to 1 and 5 mg/L) mortality was observed in the high dose group. As systemic toxicity (mortality) was observed in the acute inhalation toxicity studies with the structural analogues in rats, it is likely that the cesium potassium fluoroaluminate will also be absorbed if it is inhaled.

In the absence of substance specific quantitative data on absorption, a default (worst case) absorption value of 100% is assumed for the oral and inhalation route.

Dermal absorption

Measured data on dermal absorption of cesium potassium fluoroaluminate are not available. Solid substances will only penetrate the skin in (aqueous) solution. Cesium potassium fluoroaluminate is a salt with a water solubility of 6.0 g/L at neutral pH. Once dissolved, the salt is ionized to potassium, cesium, fluoroaluminate ions. The ions are hydrophylic and due to lack of lipophilicity, they will not have any affinity to skin (lipids). Therefore, skin absorption can only occur through the water that penetrates the skin and the maximum skin absorption is defined by the maximum water solubility of the salts and the maximum amount of water that can penetrate the skin. The maximum amount of water that can penetrate the skin is determined to be 17 µL per 1 cm2 per 24 hours (Ten Berge, W. A simple dermal absorption model: derivation and application. (Chemosphere 2009; 75(11):1440-5), which equals 6 µL per cm2 per 8 hours. Since 6 µL of water can maximally penetrate 1 cm2 of skin per 8 hours, 6 x 6 = 36 µg of ionized salt may penetrate 1 cm2 of skin per 8 hours. In an in vitro skin absorption experiment (according to OECD guideline 428), the application should mimic human exposure, normally 1 - 5 mg/cm2 (1000 - 5000 µg/cm2 ). Thus, in case the skin penetration of cesium potassium fluoroaluminate would be experimentally determined according to OECD guideline 428 using 5 mg/cm2 as exposure condition, a skin penetration of 0.72% (36/5000) would be observed maximally. Therefore a skin penetration of cesium potassium fluoroaluminate of 0.72% is considered a worse-case situation for workers.